Submitted to: Journal of Cotton Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2006
Publication Date: 12/1/2006
Citation: Saha, S., Raska, D.A., Stelly, D.M. 2006. Upland (Gossypium hirsutum L.) x Hawaiian cotton (G. tomentosum Nutt. ex Seem.) F1 hybrid hypoaneuploid chromosome substitution series. Journal of Cotton Science. 10:263-272. Interpretive Summary: The genus Gossypium is a very diverse genus with both diploid and tetraploid species. However, a very narrow germplasm base is presently being used for genetic improvement of upland cotton. The wild tetraploid cotton species are reservoirs of important genes for pest and disease resistance, and for improved agronomic and fiber traits. Gossypium tomentosum, a wild tetraploid species, endemic to dry and rocky coastal areas of the Hawaiian Islands is at risk of becoming endangered in the near future due to rapid costal development. The lack of nectaries in the leaves, bracts, and extra-floral regions in G. tomentosum contributes to the reduction of certain cotton insect populations. The narrow genetic base in Upland cotton can be improved with interspecific crosses with wild tetraploid species. Breeders face many challenges in conventional interspecific crosses including poor agronomic qualities of the progeny, distorted segregation, sterility, mote formation, and limited recombination due to incompatibility between the genomes of the two species. An alternative approach to conventional introgression is via chromosome substitution lines. Development of aneuploid plants missing different chromosome or chromosome arms from interspecific crosses are the foundation that are crucial in developing chromosome substitution lines. The difficulty in developing of such aneuploid plants varies widely among crop species and chromosomes. Here we report for the first time the development of 45 interspecific F1 monosomic (missing a complete chromosome) and monotelodisomic (missing a short or long arm of a chromosome) substitution hybrids of G. hirsutum inbred TM-1 (2n=52) with specific chromosomes and chromosome arms of G. tomentosum. Aneuploid monosomic and monotelodisomic plants were identified based on phenotypic and conventional cytogenetic techniques of meiotic metaphase I configuration analysis. These aneuploid chromosome substitution stocks are an additional resource for localization of genomic markers, for development of backcross substitution lines, and thus a stepping stone toward high-resolution chromosome-specific genetic dissection and mapping of complex traits, introgression and cotton improvement.
Technical Abstract: Interspecific germplasm introgression enables unique opportunities for genetic analysis and improvement of domesticated plants, but is commonly impeded by barriers to transmission and recombination, insufficient genetic resolution, and the difficulty of deriving economically suitable products. Such impediments is mitigated to varying extents by the breeding of chromosome substitution lines. However, the difficulty of developing such lines varies widely among crop species and chromosomes. Here, we report the development of 45 interspecific F1 monosomic (2n=51) and monotelodisomic (2n=52) substitution hybrids of Gossyium hirsutum L. inbred TM-1 (2n=52, [AD]1 genome) with specific chromosomes and arms of G. tomentosum Nutt. ex Seem., a wild cotton (2n=52, [AD]3 genome) species endemic to dry and rocky coastal areas of the Hawaiian Islands. Hypoaneuploid plants were identified based on phenotypic syndromes, and conventional meiotic metaphase I configuration analysis of acetocarmine-stained microsporocytes (pollen mother cells). Characteristics of the hybrids were largely intermediate to those of the parental species including hairy silvery-green to gray-green palmately veined leaves, a muted but distinctly sulfur-yellow corolla and yellow pollen, no central petal spot, strongly exerted stigma, and absence of nectaries and short brown seed fiber. Each hypoaneuploid F1 interspecific hybrid in the series is heterozygous for all parental nuclear polymorphisms except where G. tomentosum loci are hemizygous due to absence of a specific G. hirsutum arm segment or chromosome. These hypoaneuploid chromosome substitution stocks are an additional resource for localization of genomic markers, for development of backcross substitution lines, and thus a stepping stone toward high-resolution chromosome-specific genetic dissection of complex traits, introgression and cotton improvement.